/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/**
 * @fileoverview
 * The global object gadgets.json contains two methods.
 *
 * gadgets.json.stringify(value) takes a JavaScript value and produces a JSON
 * text. The value must not be cyclical.
 *
 * gadgets.json.parse(text) takes a JSON text and produces a JavaScript value.
 * It will return false if there is an error.
 */

/**
 * @static
 * @class Provides operations for translating objects to and from JSON.
 * @name gadgets.json
 */

/**
 * JavaScript-based implementation when window.JSON is not present.
 * Port of the public domain JSON library by Douglas Crockford.
 * See: http://www.json.org/json2.js
 */
if (!(window.JSON && window.JSON.parse && window.JSON.stringify)) {
  /**
   * Port of the public domain JSON library by Douglas Crockford.
   * See: http://www.json.org/json2.js
   */
  gadgets.json = function() {

    /**
     * Formats integers to 2 digits.
     * @param {number} n number to format.
     * @return {string} the formatted number.
     * @private
     */
    function f(n) {
      return n < 10 ? '0' + n : n;
    }

    Date.prototype.toJSON = function() {
      return [this.getUTCFullYear(), '-',
        f(this.getUTCMonth() + 1), '-',
        f(this.getUTCDate()), 'T',
        f(this.getUTCHours()), ':',
        f(this.getUTCMinutes()), ':',
        f(this.getUTCSeconds()), 'Z'].join('');
    };

    // table of character substitutions
    /**
     * @const
     * @enum {string}
     */
    var m = {
      '\b': '\\b',
      '\t': '\\t',
      '\n': '\\n',
      '\f': '\\f',
      '\r': '\\r',
      '"' : '\\"',
      '\\': '\\\\'
    };

    /**
     * Converts a json object into a string.
     * @param {*} value
     * @return {string}
     * @member gadgets.json
     */
    function stringify(value) {
      var a,          // The array holding the partial texts.
          i,          // The loop counter.
          k,          // The member key.
          l,          // Length.
          r = /[\"\\\x00-\x1f\x7f-\x9f]/g,
          v;          // The member value.

      switch (typeof value) {
        case 'string':
          // If the string contains no control characters, no quote characters, and no
          // backslash characters, then we can safely slap some quotes around it.
          // Otherwise we must also replace the offending characters with safe ones.
          return r.test(value) ?
              '"' + value.replace(r, function(a) {
                var c = m[a];
                if (c) {
                  return c;
                }
                c = a.charCodeAt();
                return '\\u00' + Math.floor(c / 16).toString(16) +
                   (c % 16).toString(16);
              }) + '"' : '"' + value + '"';
        case 'number':
          // JSON numbers must be finite. Encode non-finite numbers as null.
          return isFinite(value) ? String(value) : 'null';
        case 'boolean':
        case 'null':
          return String(value);
        case 'object':
          // Due to a specification blunder in ECMAScript,
          // typeof null is 'object', so watch out for that case.
          if (!value) {
            return 'null';
          }
          // toJSON check removed; re-implement when it doesn't break other libs.
          a = [];
          if (typeof value.length === 'number' &&
              !value.propertyIsEnumerable('length')) {
            // The object is an array. Stringify every element. Use null as a
            // placeholder for non-JSON values.
            l = value.length;
            for (i = 0; i < l; i += 1) {
              a.push(stringify(value[i]) || 'null');
            }
            // Join all of the elements together and wrap them in brackets.
            return '[' + a.join(',') + ']';
          }
          // Otherwise, iterate through all of the keys in the object.
          for (k in value) {
            if (/___$/.test(k))
              continue;
            if (value.hasOwnProperty(k)) {
              if (typeof k === 'string') {
                v = stringify(value[k]);
                if (v) {
                  a.push(stringify(k) + ':' + v);
                }
              }
            }
          }
          // Join all of the member texts together and wrap them in braces.
          return '{' + a.join(',') + '}';
      }
      return '';
    }

    return {
      stringify: stringify,
      parse: function(text) {
        // Parsing happens in three stages. In the first stage, we run the text against
        // regular expressions that look for non-JSON patterns. We are especially
        // concerned with '()' and 'new' because they can cause invocation, and '='
        // because it can cause mutation. But just to be safe, we want to reject all
        // unexpected forms.

        // We split the first stage into 4 regexp operations in order to work around
        // crippling inefficiencies in IE's and Safari's regexp engines. First we
        // replace all backslash pairs with '@' (a non-JSON character). Second, we
        // replace all simple value tokens with ']' characters. Third, we delete all
        // open brackets that follow a colon or comma or that begin the text. Finally,
        // we look to see that the remaining characters are only whitespace or ']' or
        // ',' or ':' or '{' or '}'. If that is so, then the text is safe for eval.

        if (/^[\],:{}\s]*$/.test(text.replace(/\\["\\\/b-u]/g, '@').
            replace(/"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g, ']').
            replace(/(?:^|:|,)(?:\s*\[)+/g, ''))) {
          return eval('(' + text + ')');
        }
        // If the text is not JSON parseable, then return false.

        return false;
      }
    };
  }();
}
